Pulsed Laser Spectral Pattern Detection Based On Fabry-Perot Interferometer

Doppler wind lidar was an important mean to obtain the atmospheric environment parameters.Many domestic research institutes had made breakthrough progress in the field of wind lidar.The peak area of sodium layer(approximately 91 km)and the edge of sodium layer approximately 82 and 103 km)wind field had been detected.Doppler wind lidar used a narrow-band nanosecond-pulsed laser beam as the light source.The spectral pattern was an important parameter for inversion of wind temperature data,which affected the detection accuracy and stability of lidar.Therefore,online monitoring laser spectral pattern was required.In this paper,a system based on Fabry-Perot interferometer(FPI),narrow pulse signal gate integral averager and AD modulus sampler was built which could detect the spectral pattern of pulsed laser.Online detection and real-time analysis of sodium layer wind and temperature lidar were performed.This paper mainly covered the following four parts:System Principle: According to the signal characteristic of nanosecond pulsed laser beam and the working mechanism of Fabry-Perot interferometer,a method for detecting puled laser spectral pattern was obtained,and a spectral pattern detection system of lidar was constructed;Hardware structure: A special collection of optical system was built,A voltage module with high-precision voltage output and program control,high-speed photodetector,Boxcar gated integrator and AD sampling card were selected to compose hardware system;Software Realization: The accurate control of FPI cavity length and synchronous acquisition of pulse signal were realized.Moreover,the display of system status and online data processing were achieved.Test Results and Analysis: The whole spectral pattern measurement system was tested.The measurement system was used to analyze the emission beam of the sodium layer wind and temperature lidar.The emission beam of sodium layer wind and temperature lidar was detected.The measurement result showed that the linewidth was approximately 123 MHz,which was basically consistent with the factory measurement,the high precision detection requirement of the wind laser lidar was met.This system can be mounted on the lidar for real-time monitoring of spectral pattern,provided technical support to ensure the accuracy and stability of the wind lidar.